In general, at the beginning of use of a pneumatic tire, the pneumatic tire does not sufficiently maximize the potential. This is because a mold release lubricant, which has been applied to the mold surface for the purpose of improving the releasability of the pneumatic tire from the mold in a curing process, remains on the tread surface of the pneumatic tire. Accordingly, break-in of the pneumatic tire for a certain distance is necessary to wear off the tread surface of the pneumatic tire so that the genuine tread rubber can be exposed to the outside. After the break-in, the pneumatic tire can eventually maximize the potential.
For the purpose of compensating for the lack of the performance of a tire during the break-in run, Patent Document 1 proposes the following technique. Specifically, a plurality of fine grooves with a depth of 0.1 mm to 0.8 mm, a width of 0.1 mm to 0.8 mm, and a pitch of 0.5 mm to 2.0 mm, are formed in parallel in the tread surface of a pneumatic tire. Concurrently, each of the fine grooves is inclined at 42° to 60° relative to the circumferential direction of the tire. Accordingly, the fine grooves compensate for the lack, at the beginning of use, of the braking and driving performance until the tread surface is worn out.
However, the progression of wear of the tread surface of a pneumatic tire is not uniform over the entire ground-contacting surface. For this reason, even when the above-described shallow fine grooves are provided, it is difficult for general drivers to determine whether or not the tire can maximize the potential.    Patent Document 1: Japanese patent application Kokai publication No. 2004-34903